Matching up "sitz" bone measurements with saddle sizes
How do you equate the sitx bone measurement with actual saddles widths?
I understand you are supposed to add perhaps 15-25mm to your measurement, but is that the actually total width then of the seat?
The reason I ask is that I plan to buy a saddle from some private party -- new or used -- and I mostly see total length and width of the saddle.
For example, I have a sitz bone width of 115mm. If I add a typical 20mm to that to get to 135, do I buy a saddle of that width or something wider?
Thanks.